Washington has revealed the first nuclear submarine that will deploy to Australia under the AUKUS agreement, five years after the $386 billion defence pact was signed.
The USS Colorado, a 10-year-old Virginia-class submarine, will make its new home at Western Australia's HMAS Stirling from late 2027, Defence Minister Richard Marles revealed in a joint statement with his US and British counterparts on Tuesday.
It's the first of up to four American submarines, and one from the UK, set to rotate through the base while Australian Defence Force personnel get to grips with owning and operating nuclear submarines.
But Colorado's arrival in Australia will be controversial because of outrage sparked in June over revelations the US would deliver lesser equipment than first promised.
Original AUKUS plans had Canberra receiving two used vessels and a brand new Virginia-class submarine before building one of its own in Adelaide.
The fact Washington would now be sending second-hand vessels was described as "trash" by Tasmanian independent senator and army veteran Jacqui Lambie, but ministers and top military brass at the time insisted used subs were the best option.
Prime Minister Anthony Albanese at the time assured the public AUKUS was going "full-steam ahead" despite tweaks being made to the mega-money deal, which US Secretary of War Pete Hegseth reiterated on Tuesday along with Mr Marles and UK Secretary of State Wes Streeting.
Colorado is a "fast-attack" submarine, reaching more than 46km/h, compared with Australia Collins-class subs' underwater top speed of 37km/h.
While second-hand, the Virginia class is Washington's most advanced line of attack submersibles.
The higher-speed, longer-range vessels are needed to help Australia defend its sea trade, Mr Marles has said.
"The selection of USS Colorado ... is a decisive step in strengthening collective deterrence in the Pacific," the joint statement read.
Australia's own nuclear subs will be conventionally armed, but the US has maintained a policy of ambiguity about whether or not assets rotating through the country are carrying nuclear weapons.
Being nuclear-powered means its range is effectively limited only by its crew's need for food and water.
Tuesday's statement says the AUKUS rotation arrangement will abide with all relevant non-proliferation treaties.